The solution space of sorting with recurring comparison faults

Artikel i vetenskaplig tidskrift, 2018

Suppose that n elements shall be sorted by comparisons, but an unknown subset of at most k pairs systematically returns false comparison results. Using a known connection with feedback arc sets in tournaments (FAST), we characterize the solution space of sorting with recurring comparison faults by a FAST enumeration, which represents all information about the order that can be obtained by doing all comparisons. An optimal parameterized enumeration algorithm for FAST also works for the more general chordal graphs, and this fact contributes to the efficiency of our representation. Then, we compute the solution space more efficiently, by fault-tolerant versions of Treesort and Quicksort. For rare faults the complexity is close to optimal. We propose propose directions of further research, revolving around decision diagrams for sorting with recurring faults.